At least one other member of staff knew the boy was getting smacked, they at the time either thought it was acceptable or kept quiet anyway. The boy’s mother was confident at least that the headmaster was not going to be getting into trouble as she was happy to tell myself and several other people about it.
I do not know if the Headmaster felt confident that he wasn`t breaking the law or just confident that no one would be reporting him. If it was the latter then he was correct, several people knew about it yet none reported him.